Science Acids and Bases

Properties of Bases

1. bitter taste 2. feel slippery 3. conduct electricity when dissolved in water

Properties of Acids

1. sour taste 2. conduct electricity when dissolved in water 3. react with metals to produce hydrogen gas

Why is acidity is an important?

Acidity is an important factor for living things because most can survive only within a relatively narrow range of acidity.

If you were to combine acid and base solutions, what products do you think would be produced?

Combining acid and base solutions produces water and a neutral ionic compound.

What are examples of strong or weak base?

For example, sodium hydroxide (NaOH), a base in drain cleaner, is a strong base because all of it breaks down into ions when it dissolves in water. Calcium carbonate (CaCO3), a base in antacids, is a weak base because only a small percentage of it breaks down into ions in water.

Detecting Bases

If you place a few drops of a base on a strip of red litmus paper, the paper will turn blue.

What is salt?

Ionic compound formed when an acid and base react.

Bases

Ionic compounds that produce negative hydroxide ions (OH-) when dissolved in water. Ex. sodium hydroxide (NaOH)

What will happen if you place a few drops of acid on a strip of blue litmus paper?

The paper will turn red.

pH scale

The strength of acids and bases is measured on a scale

What is acidity and what causes it?

The strength of an acid or base is called acidity. It depends on how much of the substance breaks down into ions when it dissolves in water.

What is the chemical formula for the break down of a acid?

HCl →H2O H+ + Cl-

What can you use to detect an acid?

Indicators because they change color when acids come into contact with them. Ex. litmus, Red cabbage juice

Acids

Ionic compounds that produce positive hydrogen ions (H+) when dissolved in water. Ex. hydrogen chloride

The pH scale is based on powers of ten.

It's important to realize that the pH scale is based on powers of ten. For example, a solution with a pH of 8 is 10 times more basic than a solution with a pH of 7, and a solution with a pH of 9 is 100 times more basic than a solution with a pH of 7.

Ions (refresher question)

atoms that have become charged particles by gaining or losing electrons.

Uses of Bases

They are found in many cleaning products, deodorant and in concrete.

What does a pH value greater than 7 indicate?

A pH value greater than 7 indicates a basic solution. The higher the pH value is, the stronger the base. The strongest bases, such as drain cleaner, have a pH value close to 14.

What does a pH value less than 7 indicate?

A pH value less than 7 indicates an acidic solution. The lower the pH value is, the greater is the concentration of hydrogen ions and therefore the stronger the acid. The strongest acids, such as battery acid, have pH values close to zero.

What has a pH value of 7?

A pH value of 7 indicates a neutral solution.

How are acids and bases similar? How are they different?

A property that is shared by bases and acids is the ability to conduct electricity when dissolved in water. Some ways bases and acids are different is that acids taste sour whereas bases taste bitter. Also, acids but not bases react with metals.

How is the strength of acids is measured?

A scale called the pH scale. The pH value of a solution represents its concentration of hydrogen ions.

How much more acidic is a solution with a pH of 4 than a solution with a pH of 7?

A solution with a pH of 4 is 1000 (10 × 10 × 10, or 10 to the 3rd) times more acidic than a solution with a pH of 7.

Why pH Matters

Acidity is an important factor for living things. For example, many plants grow best in soil that has a pH between 6 and 7. Fish may also need a pH between 6 and 7. Certain air pollutants form acids when dissolved in water droplets in the air. This results in acid fog and acid rain.

How is acidity measured?

Acidity is measured by pH, which is the concentration of hydrogen ions in a solution.

What are examples of strong or weak acids?

For example, sulfuric acid (H2SO4), which is found in car batteries, is a strong acid because nearly all of it breaks down into ions when it dissolves in water. On the other hand, acetic acid (CH3CO2H), which is the acid in vinegar, is a weak acid because less than 1 percent of it breaks down into ions in water.

What is the chemical formula for the break down of a base?

NaOH →H2O OH- + Na+

neutralization reaction

Reaction of an acid and a base that produces water and a salt, both of which are neutral in acidity.

Uses of Acids

Sulfuric acid is used to manufacture a variety of different products, including paper, paint, detergent and car batteries. Nitric acid and Phosphoric acid: are used to make fertilizer. Hydrochloric acid: is used to clean swimming pools, bricks, and concrete. Hydrochloric acid is in your stomach.